Building Harlequin's Moon is one of those "the less famous writer does the real work" collaborations. Brenda Cooper's thank-you notes at the beginning make it clear this was mostly her baby, shepherded not only by Niven but apparently hordes of contributors to Niven's website forums. So, if it's apropos to consider this Cooper's debut novel, then let me say what a fine debut it is. Building Harlequin's Moon is what the best hard SF ought to be: bristling with stimulating scientific ideas while never losing sight of the humanity at the core of every scientific endeavor. It's an absorbing adventure of survival in the harshest environments of deep space, and a compassionate drama about how the best laid plans of AI's and men can go horribly awry.

The premise is that an exodus of humanity from an Earth and solar system rendered unlivable by out-of-control nanotech and AI's has gone fubar. The John Glenn, one of three privately funded vessels on its way to the distant colony world of Ymir, has suffered unforeseen technical problems and burnt out its last remaining antimatter fuel getting to a tiny system comprised mostly of lumbering gas giants. The High Council who run the vessel have no choice but to undertake an unprecedented project to save themselves. In an undertaking that lasts over 60,000 years — managed by Council who go in and out of cold sleep as necessary, a process that rejuvenates them when they awaken — they herd together a number of tiny moons surrounding a gas giant they've dubbed Harlequin, and literally bash them together to make one livable moon they name Selene. With Harlequin itself heated up to provide additional warmth to the new world, Selene is slowly terraformed.

But the Council's goal is not to settle Selene, it's simply to make the new moon a production facility to replenish their antimatter. Selene is populated by descendents of the "Earth Born." The Children, or Moon Born, are taught how to terraform their world, and learn to view the Council nearly as gods. But they learn nothing of humanity's vast history, and, though they aren't mistreated, they're effectively little more than slaves. There is, naturally, an undercurrent of tension. They know the High Council intend to go on to Ymir when the project is done. But what if they leave the Moon Born behind? What will the Children do? Can they even survive?

Some of the Council — those who stay in the John Glenn in orbit — are indifferent to the Children, but those who work closely with them on Selene's surface inevitably develop a bond. Our heroes are Gabriel, one of the Council directly responsible for creating Selene over sixty millennia of intermittent cold sleep shifts, and Rachel Vanowen, a 17-year-old Moon Born girl determined to do right by the Council and faithful in her belief the Council have the Children's best interests at heart. She gets a reality check when Gabriel brings her up to the John Glenn ostensibly for instruction on how to become one of Selene's community leaders. In a turn of events even Gabriel did not expect, the two of them end up in cold sleep for twenty years.

It's effectively moving the way Cooper is able to convey the emotional trauma this girl-interrupted scenario has on Rachel. It avoids collapsing into melodrama. Rachel returns to a Selene deeply changed. Her friends are all much older, one has died, the boy she loved is now nearly forty with a family of kids almost her age, and the Children overall are becoming more and more suspicious of the Council's motives. One, Andrew, punished for playing a nasty prank on Rachel when they were young, has grown into an embittered man who exerts a growing influence over a small coterie of paranoid followers. It looks as if tensions between ship and moon are about to boil over. And if they do, the fragility of their existence could mean it won't take much for a minor dustup to turn into disaster.

That precarious existence is always at the forefront of the story, creating a palpable air of suspense every time even the tiniest problem arises. And things are no better or safer for the Council aboard their ship. They are torn by internal conflicts, and no one will quite give voice to the possibility that the paradise on Ymir they hope to reach someday may not even exist. Only Gabriel and a few others entertain the likelihood they may be the last humans in the universe. And while they all know they need the Children to realize their goals, the fact that the Children are becoming increasingly aware of this too is causing more than a little nervousness. Two groups of people, rulers and followers, each clinging to what are basically pie-in-the-sky future hopes and neither trusting the other — well, this is a recipe for turmoil.

Cooper's gift for creating rich characters to whom you immediately feel drawn lifts Building Harlequin's Moon above the kinds of hard SF in which the Big Ideas take precedence and the characters are afterthoughts whose function is merely, as in the formula popularized by Analog, to Solve the Problem. Rachel is a perfect Everyperson, a heroine who rises to the occasion not by being traditionally heroic but by realizing that problems only do get solved when you have grown enough to make your own decisions. When everything goes pear-shaped towards the book's exciting climax, she learns, as all classic heroes must, that making the right choice is never a matter of perfect moral clarity.

If I have any nitpicks about this book, it's that the midsection sags rather markedly. And the whole book does go on a little long, particularly in the service of what might strike a lot of readers as nothing much more than a "can we all just get along?" theme. But if that's all this novel is about in the end, I cannot complain about the sensitive, human, and often very thrilling way Cooper — with the help of one of SF's masters — managed to tell it. But I don't really think the book's themes are summed up that simplistically. The novel is really about the importance, not merely of cooperation and communication, but understanding, and not being so absorbed in your own goals that you fail to see how your actions affect others. It's about how those who think crises are best kept at bay by exerting ever more stringent forms of control eventually end up causing more crises than they contain. It's a theme that even applies to the ship's AI, who plays a vital role in events though most of the Council retain their fear of AI from their experiences on Earth and have limited its potential accordingly. That artificial intelligence went bad in the solar system in part because, again, neither AI's nor humans really made the effort to understand each other becomes increasingly evident.

I know I'm going to miss Rachel and her family and friends now that I've finished this story. That's more than I can say for the heroes of most multibook series I plow through. A recommended read, from a new talent whose career I hope to see building and building.